Electric cable



C. E. BENNETT ELECTRIC CABLE Nov. 26, 1940.

Filed Sept. 11, 1937 NOM- MEGA ENC M57414 5 72PM W W W/ W a L w w v 0 g0 m 7 we r M Z 4 2 WM M 1 M 5 1 6 I W 0/1. //VPEE6 M475; PAPEe 85g;INVENTOR mwm Patented Nov. 26, 1940 UNITED STATE FFIE 2.222.932istccrnio one Jersey Application September ill, 193?, Serial No. 163,372

2 (Claims.

This invention relates to an improvement in electric cables,particularly to high voltage cables which are installed in pipe lines.

These cables as heretofore constructed are 5 usually composed of copperconductors insulated with laminated paper insulation. Over thisinsulation a suitable electrostatic shielding tape is applied and thensome kind of protective covering such as braid, canvas tape or similarmaterials. This outer covering protects the paper insulation againstabrasion when pulling the cable into the pipe line.

It has been found that the frictional resistance to pulling such cablesinto a pipe when a canvas or similar covering is used makes it ditficultto pull long lengths, of the order of several thousand feet for example.

I have found that by installing a metallic covering instead of thecanvas the frictional resistance to pulling in is very materiallyreduced. Actual tests have indicated a. coeflicient of friction one-halfthat of a non-metallic covering. It has been suggested to concentricarmor the exterior of the cable, but this requires considerable materialand the added weight tends to offset the gain in lessening thecoeflicient of friction.

In the proposed construction of this invention I employ a half roundhigh resistance or 80 non-magnetic metal strip wound spirally about thecable with gaps say of one-half inch between successive turns. When theshielding tape is installed a very thin cotton or paper tape isinterlocked between successive turns of the shield- 85 ing tape, the Dsection or half round outer nonmagnetic strip touching and makingcontact with the shielding tape wherever the two metallic surfaces cometogether. This construction therefore short circuits the shielding tapeat 40 numerous intervals, the half round strip contacting the wall ofthe pipe line in which the cable is installed. The shielding tape inefiect, therefore, is grounded continuously throughout its length.

Where shielding tape is installed with a paper or other insulated spacebetween successive turns and then covered with canvas, as above.

5 be of such value that damage may be done to the cable insulation.Under some conditions a sparking voltage continuously induced wouldsooner or later deteriorate the insulation.

The disadvantages and drawbacks referred to in the preceding paragraphare overcome by the present invention.

An embodiment of the invention is illustrated in the accompanyingdrawing, wherein:

Fig. 1 is a cross sectional view of a three phase cable of the presentinvention, installed in a pipe line; and

Fig. 2 is an elevational view of one of the ca bles of Fig. 1 with partsbroken away at different levels "for clarity of illustration.

Referring to the drawing in detail, 2 designates an iron or steel pipeline in which the cable is to be installed. A three phase system hasbeen illustrated, the separate cables being designated i, 6 and 8respectively.

These cables are alike and one has been illustrated in detail and on alarger scale in Fig. 2.

With reference to this figure of the drawing, ll] designates theconductor. which is insulated with oil impregnated oil filled paper tapel2. About this insulation is spirally wound electrostatic shielding tapeI4. This tape may be thin copper for example, and it may if desired beinterlocked with a very thin cotton or paper tape.

Over the shielding tape II and contacting therewith, I spirally apply ahalf round or D section non-magnetic metal strip Hi. This is appliedwith its convex'face outward, the flat face lying in contact with theshielding tape I4.

Extending lengthwise of the cable over the strip I6 is a. crlmped pianowire l8, and about the whole assembly is applied an outer sheath, as forexample a thin lead sheath 20. This sheath is removed by ripping thesame open with the piano wire l8 as the cable is drawn into the pipeline 2.

After the three phases have been pulled into the pipe line the latter isfilled with oil under pressure designated 22.

It will be appreciated that by crimping the piano wire l8 the cable maybe reeled for shipment without endangering the wire. It will be apparentalso that by employing a half round strip over the shielding tape thefrictional resistance to pulling the cable into the pipe line is verymaterially reduced as compared with canvas and the like, with the addedadvantage that, inasmuch as this half-round strip contacts the metalpipe line and the shielding tape, the latuously throughout its entirelength.

ter will be short circuited substantially contin- It is to be understoodthat changes may be made in the details of construction and arrangementof parts above described within the purview 01' this invention.

What I claim is:

1. An electric cable comprising in combination an insulated conductor,electrostatic shielding tape interlocked with a non-metallic tapewrapped about the insulation, and a solid metal strip of substantiallyhalt-round cross section wrapped about the said electrostatic shieldingwith its flat face in contact with the shielding.

said wire to remove the same from the cable 1 when the latter isinstalled.

CHARLES E. BENNETT.

